Also, he has his own memory orbs like the other emotions, though his are black. Judging by the name, you can probably infer that he gives his controller the rush of euphoria from causing misery or harm to others (or simply seeing bad things happen to bad people, and giving the feeling that it's deserved). Understandably, the other emotions have to keep him in check, though most of the time he's kept under lock and key and only occasionally fed in various ways to keep him sated so he doesn't break out and cause more destruction than if he were just outright released.